STRUCTURAL EVOLUTION OF UNDERCOOLED SINGLE-PHASENi-2wt%Pb MONOTECTIC ALLOY

The structural evolution of undercooled single-phase Ni-2wt%Pb monotectic alloy was systematically investigated by using the method of molten glass denucleating combined with superheating cycle. Within the achieved undercooling range e of 22 to 280K, the solidification structure undergoes three changes at 22K, 88K and 187K, respectively. With the increase of undercooling, common dendrites, the first class granular grains, nudercooled dendrites and the second class granular grains come out one after the other. Analytical results show that the granulation mechanism of the first class granular grains is owing to dendrite remelting and recrystallization, and the second is owing to dendrite break-op and recrystallization.